The present invention relates to an improved implantable defibrillator.
Defibrillators ar electronic devices capable of delivering sufficient energy to the cardiac muscle to convert an erratic heart rhythm (ventricular fibrillation) to a normal heart rhythm. Defibrillators are used in a variety of situations where there is a possibility that a person may have life threatening ventricular arrhythmias (ventricular tachycardia or ventricular fibrillation).
It is known in the art that cardiac defibrillation may be achieved by applying electrodes to a person's skin, on either side of the heart, and applying electric energy to the electrodes. Such a system is used where the need for defibrillation is not foreseeable. However, in instances where the need for defibrillation is due to a pathological state, it is preferable to use an implantable defibrillation system that can automatically apply the necessary electrical discharge to the heart when the need arises.
Implantable defibrillators of the type above-mentioned are known in the art. These implantable defibrillators generally include an energy source, such as a battery, a capacitor to store energy for delivery to the heart and electrodes to deliver the energy to the heart. Additionally these systems include a sensor to determine when defibrillation is needed.
Pacemakers, in contrast to defibrillators, are electronic devices which pace the heart when the heart rate is too slow. Pacemakers, in contrast to defibrillators, use a small amount of energy. The energy requirement of a pacemaker is a fraction of the energy required to defibrillate the heart.
In presently known implantable defibrillator systems, ten to twenty-five joules of energy is necessary to defibrillate the heart. In order to achieve this energy delivery, fairly large components are needed. Thus it is currently necessary to open the chest to implant the defibrillator and place at least one electrode on the heart. This is major surgery requiring anesthesia and thus has attendant risks.
Major surgery creates risks which should be avoided when possible. This is of particular significance in a patient who is a candidate for an implantable defibrillation system since such patients are already in less than optimum health.
Accordingly it is an object of the present invention to provide an implantable defibrillator which does not require open-chest surgery for implantation.
It is yet another object of the present invention to provide such an implantable defibrillator which can defibrillate the heart using less energy than previously known defibrillators. That is, the purpose is to lower the defibrillation threshold.